The specific aim of this proposal is the fifth meeting of participants working towards the implementation of the International Breast Cancer Screening Data Base to provide a mechanism for the comparison of data from population-based screening programs for breast cancer in various countries, in order to facilitate the most effective and efficient contribution of screening to breast cancer control worldwide. In the Fall 1994 meeting, the group has the following objectives: l. To facilitate the collection of comparable data regionally, nationally and internationally on: screening policies recommended, target groups for screening, women screened, outcome of screening examinations, follow-up of screened women, trends in breast cancer incidence and mortality, and description of quality assurance applications. 2. To provide a standard set of tables and definitions to countries considering the establishment of population-wide breast screening programs. 3. To facilitate international agreement on the intermediate and ultimate outcome measures utilizable for the evaluation of the effectiveness of breast cancer screening, and to encourage the collection of such measures. 4. To compare the effectiveness (depending upon agreed upon measures) of different regional and national screening policies utilizing the data collected. 5. To provide data to contributing regional and national programs on the effectiveness of their program in comparison with other contributing countries. 6. To develop agreed upon mechanisms for a country to determine the: costs of screening, medical care costs generated by screening, and the medical care costs saved by screening; and based on these: the cost-effectiveness of breast cancer screening. 7. To utilize the standardized mechanisms for determining the cost- effectiveness of breast cancer screening in comparison of different programs regionally and nationally, and to report the results of such an evaluation back to the contributing programs. 8. To encourage communication among countries about additional research questions to make research findings more comparable.